Bridge plate lifting device



' J y 2 97 M. AKERS 3,521,577

BRIDGE PLATE LIFTING DEVICE Filed Dec. 28, 1967 5 Sheets-Sheet 1 INVENTOR. Q0/5527 M AKEQS R. M; AKERS- BRIDGE PLATE LIFTING DEVICE 5 Sheets-Sheet 2 Filed D80. 28, 1967 INVENTOR. Pa/sazr M Aka-es July 21, 1970 R. M. AKERS BRIDGE PLATE LIFTING DEVICE Filed Dec. 28, 1967 3 Sheets-Sheet 3 United States Patent Office 3,521,577 Patented July 21, 1970 US. Cl. 105-458 18 Claims ABSTRACT OF THE DISCLOSURE A device for supporting, and aiding in lifting, a bridge plate of the type used to span the space between two coupled railroad cars comprising lifting arm means including a lifting arm adapted to contact the underside of the bridge plate, and an elongated member connected to one end of the lifting arm or formed integrally therewith and extended concentrically through a cylindrical housing. A torsion spring is mounted within the housing and connected to the elongated member so as to be loaded in tension when the arm is pivoted and the elongated member is rotated about its axis. The ends of the cylindrical housing are closed by end plates, and spring anchoring and hub assemblies are located Within the housing, and function to connect one end of the torsion spring to the elongated member, and the other end of the torsion spring to one of the end plates. The spring anchoring and hub assembly which is connected to one of the end plates can be detached therefrom, and is accessible from outside the housing to permit it to be rotated a predetermined amount relative to the end plate before its securement thereto so as to preload the torsion spring to a selected degree.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to spring-biased counterbalancing devices. More particularly, but not by way of limitation, the present invention relates to a device for assisting in the manual lifting of heavy, metallic cargo bridge plates from a space spanning position between two railway cars, or between a loading dock and cargo vehicle, and to a second, retracted or inoperative position in which the device retains the bridge plate in a vertically extending position.

Brief description of the problem giving rise to the invention With the evolution of the piggyback method of cargo transport in which large trailer vehicles are carried over long distances on railroad flatcars, a need has developed to provide structurally strong, easily operated bridge plates which can be folded down from a vertically extending, inoperative position, to a horizontally extending position spanning the space between adjacent flatcars to permit the trailers to be moved from one car to the next across the bridge plate. The structural strength which must characterize these bridge plates necessarily requires them to be relatively heavy, and it is therefore necessary to provide some type of lifting or counterbalancing device which will permit lifting or lowering of the bridge plate to be accomplished manually with a minimum amount of effort and maximum safety. Such bridge plate lifting device must be capable of retaining the bridge plate in a vertically extending, inoperative position despite large forces acting on it at the time of the impacts arising from the switching and coupling of cars. The lifting device must also be compact and easily mounted on the forward end of the fiatcar, and must be very strong structurally to withstand the very rough and severe treatment to which such cars are themselves generally subjected in use. Finally, due to variations in the weight of bridge plates in use,

it is highly desirable that the device be capable of adjustment of the magnitude of the counterbalancing force which it exerts, so as to best accommodate it to different types of bridge plates with which it may be used.

Brief description of the present invention The present invention provides a bridge plate lifting device which is compact, mechanically strong, reduces to a very large extent the manual force required to raise a horizontally extending bridge plate from a horizontally extending to a vertically extending position, and which is safe to use. Broadly described, the invention comprises an elongated lifting arm which is connected to, or formed integrally with, an elongated member extended concentrically through a tubular housing. The elongated member can be merely an extension of the lifting arm, or a separate member, and is connected through a spring anchoring hub assembly located inside the housing to one end of a helically wound torsion spring which concentrically surrounds the elongated member. The other end of the torsion spring is connected to a second spring anchoring hub assembly which can rotate freely around the longitudinal axis of the elongated member, and which can be secured in a predetermined position relative to the cylindrical housing to preset the tension of the torsion spring. Suitable mounting brackets are secured to the tubular housing to permit the device to be mounted on a flatcar or loading dock.

In a preferred embodiment of the invention, the free end of the lifting arm outside the tubular housing journals a roller adapted to contact the bridge plate during use of the device, and the tubular housing is closed at its opposite ends by a pair of end plates, one of which is adapted to be connected to the described second spring anchoring hub assembly when the latter element has been rotated through a preselected arc to preset the tension in the torsion spring.

From the foregoing broad and general description of the invention, it 'will have become apparent that it is an important object of the invention to provide a bridge plate lifting device which can be quickly and easily secured to a loading dock, railroad car, or the like for the purpose of providing a smooth functioning, mechanically rugged counterb'alancing action to aid in raising and lowering a heavy bridge plate secured to such dock or railroad car.

An additional object of the invention is to provide a bridge plate lifting device which can be manufactured and assembled with a minimum of expense and difiieulty.

A further object of the invention is to provide a bridge plate lifting device which can be easily adjusted in the force which it will exert upon a bridge plate so as to accommodate the device to bridge plates of varying weight and force requirements.

Another object of the invention is to provide a bridge plate lifting device which can retain a heavy bridge plate in a retracted, vertically extending position on a moving railroad car at all times during nonuse of the bridge plate, despite subjection of the plate to inertial forces of large magnitude tending to pivot the plate downwardly at such time as the railroad car on which it is mounted strikes 'another car in the manner which occurs during switching, coupling and the like.

Yet another object of the invention is to provide a compact and sturdily built bridge plate lifting device which reduces vibration of internal parts previously used in such devices, and retards wear encountered by hinges and locks used bothin the lifting device itself, and in the bridge plate with which it is used.

Yet another object of the invention is to provide a bridge plate lifting device which effectively counterbalances a heavy bridge plate in such a manner as to reduce the total amount of force which must be applied to the bridge plate to return it from a folded down, load-carrying position to a retracted, inoperative position.

In addition to the foregoing described objects and advantages, additional objects and advantages will become apparent as the following detailed description of preferred embodiments of the invention are read in conjunction with the accompanying drawings which illustrate the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in elevation of a pair of coupled railway flatcars illustrating the bridge plate lifting device of the present invention secured to one end of one of the cars and retaining a bridge plate in a retracted or elevated status.

FIG. 2 is an end elevation view of one of the flatcars depicted in FIG. 1 illustrating the bridge plate lifting device of the invention mounted thereon.

FIG. 3 is a longitudinal sectional view taken through the center of the bridge plate lifting device of the invention and illustrating the lifting arm of the device partially in elevation and partially in section.

FIG. 4 is a detailed sectional view of one end portion of the bridge plate lifting device of the invention with such section being taken in a plane extending at an angle of 90 with respect to the plane of the section in which the view of FIG. 3 is taken.

FIG. 5 is a sectional view taken along line 5--S of FIG. 3.

FIG. 6 is an end elevation view of the bridge plate lifting device shown in FIG. 3 as the device appears when viewed from the end thereof opposite the end from which the lifting arm projects.

FIG. 7 is a longitudinal sectional view similar to FIG. 3, but illustrating a different embodiment of the invention.

FIG. 8 is a sectional view taken along line 88 of FIG. 7.

FIG. 9 is an end elevation view of the bridge plate lifting device shown in FIG. 7 as this embodiment of the invention appears when viewed from the end of the lifting device opposite the end from which the lifting arm projects.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Referring initially to FIG. 1 of the drawings, the bridge plate lifting device of this invention is illustrated therein and is designated generally by reference number 10. The bridge plate lifting device 10 is shown as attached to the front end of a railroad flatcar 12 which is coupled in conventional fashion to a second flatcar 14. The flatcar 12 carries on its upper surface adjacent its end which is connected to the flatcar 14, a bridge plate 16 of conventional construction. The bridge plate 16 is hinged at one of its edges to the flatcar 12 and can be pivoted downwardly about its pivotal axis so as to span across the space between the flatcars 12 and 14. The bridge plate lifting device 10 of the present invention functions to retain the bridge plate 16 in its retracted, upwardly extending position when it is not in use, and to increase the ease with which the bridge plate may be manually lowered to its spanning position and later retracted to its inoperative, vertically extending position, as will be hereinafter described in greater detail.

The construction of the bridge plate lifting device 14) is illustrated in detail in FIG. 3. The lifting device 10 includes an elongated lifting arm 18 which is preferably of substantially circular cross-sectional configuration and is characterized in being angulated in two planes over its length as best illustrated in FIGS. 1-3. The lifting arm 18 is preferably bent through a right angle near its upper end 18b, and through a substantially smaller angle intermediate its length in order to facilitate proper engagement with a bridge plate during operation of the device. Near its upper end 1817, the lifting arm 18 has journaled thereon a roller which engages and rolls along the lower surface of the bridge plate 16 during operation of the bridge plate lifting device as illustrated in FIG. 1.

As depicted in FIG. 3, the roller 20 has extending axially therethrough a bore 22 to permit the roller to be slidingly passed over the end portion of the lifting arm 18. The bore 22 has a circumferential groove 23 formed in the central portion thereof to accommodate a pair of spherical bear ing elements 26. Two smaller circumferential grooves are spaced axially along the bore 22 and on opposite sides of the groove 24 for the accommodation of a pair of annular sealing rings 28. A transverse passageway 30 is formed diametrically through the lifting arm 18 in line with the circumferential groove 24 and a helical spring 32 is positioned in the passageway to bias the spherical bearing elements 26 outwardly into the circumferential groove 23. A circumferential groove (not visible) is also formed around the periphery of the lifting arm 18 in alignment with the circumferential groove 24. An axially extending passageway 36 is formed in the outer end portion of the lifting arm 18 and communicates with the transverse pas sageway 30 to permit a lubricant to be introduced through a suitable lubricant fitting 38 to the passageway 32 and thence to the spherical bearing elements 26.

The end 18a of the lifting arm 18 is extended through an arm receiving socket 40 formed diametrically through an elongated member which, in the illustrated embodiment, is a tubular sleeve 42. It will be noted in referring to FIG. 4 that the outside diameter of the lifting arm 18 is slightly larger than the inside diameter of the tubular sleeve 42 so that when the end portion of the lifting arm is passed through the arm receiving socket 40, an enlarged surface area of contact is attained between the arm and the sleeve. This arrangement imparts greater structural strength to the connection and permits the lifting arm to be slightly out of round without detrimentally affecting the connection between this arm and the sleeve. A tapered pin 44 is extended through the sleeve 42 and the arm 18 to complete the connection of these elements and they may be further secured by welding if desired.

The tubular sleeve 42 extends parallel to the axis of the roller 20 and has the major portion of its length positioned concentrically within a tubular, preferabl cylindrical, housing 46. The sleeve 42 is journaled in this position relative to the housing 46 by a pair of end plates 48 and 50, and a pair of spring anchoring hub assemblies designated generally by reference numerals 52 and 54. The end plates 48 and 50 are each dimensioned to fit relatively tightly within the open ends of the cylindrical housing 46, and are welded or otherwise suitably secured in this position. The end plate 48 is centrally apertured to accommodate the sleeve 42 and is radially relieved adjacent its central aperture by an axially extending circumferential relief which accommodates a bushing or bearing 56. The bushing 56 may be constructed of bronze, Teflon or any other suitable material of relatively high mechanical strength and low friction properties. A suitable annular sealing ring 58 is also provided in the relief at one end of the bushing 56 to prevent leakage of a lubricant as hereinafter described.

For the purpose of supplying a fluid lubricant to the bearing 56, a circumferential groove 60 around the sleeve beneath the bearing is placed in communication with the interior of the sleeve by a pair of radial ports 62. A lubricant chamber is then formed in the interior of the tubular sleeve 42 by positioning a partition cap 64 between the ends of the sleeve 42 so that a closed or confining chamber exists between this cap and the lifting arm 18. A lubricant may be introduced to this chamber through a suitable lubricant fitting 66. In the event that the outside diameter of the lifting arm 18 should be undersized with respect to the inside diameter of the tubular sleeve 42, a closure cap 68 may be snapped into a cooperating groove formed in the end of the sleeve 42 to complete formation of the lubricant chamber, or such closure cap may be used for the sake of improved appearance and to prevent the ingression of dirt, water and other deleterious materials to the interior of the sleeve.

After passing through the end plate 48, the sleeve 42 extends through the spring anchoring hub assembly 52. The spring anchoring hub assembly 52 includes a relatively large diameter disk-shaped anchor plate 72 and a relatively smaller diameter hub 74 which is formed integrally with the anchor plate and extends axially along, and surrounds, the tubular sleeve 42. A tapered securing pin 76 extends through aligned apertures in the hub 74 and the sleeve 42 to key the spring anchoring hub assembly 52 to the sleeve 42 for rotational movement therewith as hereinafter described. It will be noted that the tapered securing pin 76 secures the spring anchoring hub assembly 52 to the tubular sleeve 42 at a position such that the anchor plate 72 is spaced from the end plate 48. It will be further noted that the anchor plate 72 is apertured adjacent its outer periphery to provide an aperture 78 through which one end of a helically wound torsion spring 80 may be extended. A cotter key 82 is passed through the end portion of the torsion spring 80 which is on the opposite side of the anchor plate 72 from the main portion of the torsion spring.

The helically wound torsion spring 80 concentrically surrounds the tubular sleeve 42 and is retained in this alignment by the hub 74 which extends a short distance into the torsion spring. The opposite end of the torsion spring 80 extends over and around the outside of a hub 84 which projects from, and is formed integrally with, an anchor plate 86 of the spring anchoring hub assembly 54 positioned in the opposite end of the housing 46 from the spring anchoring hub assembly 52. The anchor plate 86 is apertured near its outer periphery to provide an aperture 88 through which the second end of the torsion spring 80 extends. A cotter key 90 is extended through the end portion of the torsion spring 80 which extends through to the aperture 88 and this end portion and the cotter key are located in a relieved portion 92 provided in the outer face of the anchor plate 86 (see FIG.

The end of the tubular sleeve 42 which is disposed inside the cylindrical housing 46 is journaled in the hub 84 of the spring anchoring hub assembly 54 by means of a suitable bushing or bearing 96 which is retained in position between the sleeve and the hub by a suitable annular retaining ring 98. An annular sealing ring 100 is provided between the end of the sleeve 42 and the inner periphery of the anchor plate 86 and abuts a radially extending shoulder 102 formed at the end of the central bore in the hub assembly 54. For the purpose of maintaining the bearing 96 in a lubricated state, a circumferential groove 104 is formed around the outer periphery of the sleeve 42 adjacent the bearing 96 and a pair of radial ports 106 places the groove 104 in communication with the hollow interior of the sleeve. A partition cap 108 is then pressed into the interior of the sleeve 42, and a second partition cap 110 carrying a lubricant fitting 112 is pressed into the sleeve 42 a lesser distance to define a sealed chamber into which lubricant may be introduced through the fitting 112 to supply the bushing sleeve 96 through the ports 106 and circumferential groove 104.

On the opposite side of the anchor plate 86 from the hub 84, the spring anchoring hub assembly 54 includes an axially extending wrench fitting 114. The wrench fitting 114 projects through a central aperture 116 formed in the end plate 50, and is itself provided with a central, axially extending wrench socket 118 which is preferably of hexagonal cross-sectional configuration to permit a wrench of a mating configuration to be inserted therein as hereinafter described. It should be noted that the wrench receiving socket 118 extends into communication with the bore of the spring anchoring hub assembly 54 so that the lubricant fitting 112 is accessible through the wrench receiving socket.

In referring to FIG. 5 of the drawings, it will be noted that the face of the anchor plate 86 which is opposed to,

or faces, the end plate 50 is provided with a pair of bolt holes 120. The bolt holes 120 are preferably spaced in a circumferential sense from each other around the anchor plate 86 by about 180 of arc and are spaced about of are from the notch or relief 92 which accommodates the end of the torsion spring 80 and cotter key 90. In referring to FIG. 6, it will be noted that the end plate 50 is provided with a plurality of'circumferentially spaced bolt holes 122 which, in the illustrated embodiment, are shown as being disposed on a spacing about 30 of are around the end plate 50. It should be pointed out that the bolt holes 122 in the end plate 50 are each positioned substantially the same radial distance from the center of the end plate as the radial spacing of the bolt holes 122 in the anchor plate 86 so that alignment can be obtained between a selected pair of the bolt holes 122 in the end plate and the bolt holes in the anchor plate. Suitable bolts 124 can thus be passed through the aligned bolt holes 120 and 122 to secure the end plate 50 to the anchor plate 86.

To facilitate the securement of the bridge plate lifting device 10 of the invention to a stationary surface, such as the front end of a railroad car, a pair of mounting brackets 126 and 128 are provided. The mounting brackets 126 and 128 are identical in construction, and each includes a housing receiving plate 130 which has secured to the lower edge thereof, a pair of oppositely projecting base flanges 132 and 134. As shown in FIG. 3, the base flanges 132 and 134 are apertured to permit bolts 136, screws or other suitable fastening devices to be extended therethrough into a structural member 138 upon which the bridge plate lifting device is to be mounted (as shown in FIGS. 5 and 6).

OPERATION It may be pointed out at the outset that, in the fabrication of the bridge plate lifting device 10 of the invention, the length of the lifting arm 18 will be adjusted in a predetermined manner so as to best adapt the device to exerting the desired force and leverage on bridge plates which may vary over a certain range in their total weight. Thus, a longer lifting arm 18 may be employed for relatively heavy bridge plates. The same preselection is utilized in determining the size and properties of the torsion spring 80 which will be utilized in the device.

When the device has been assembled in the manner depicted in FIG. 3, it is mounted on one end of a railroad flatcar adjacent a bridge plate which is pivotally secured to the upper surface of the flatcar. The manner of mounting and the location of the bridge plate lifting device 10 are best illustrated in FIGS. 1, 2 and 6 of the drawings. It will be noted that the angulation of the lifting arm 18 permits the roller 20 carried at the upper end 1817 of the arm to bear against the lower surface of the bridge plate 16 and that the bridge plate extends substantially vertically at such time as the plate is biased to its retracted or inoperative position by the bridge plate lifting device. The lifting device 10 is secured to the forward end of the flatcar 12 by means of suitable bolts 136 passed through bolt holes located in the flanges 132 and 134 of the mounting brackets 126 and 128. It should be pointed out that the bridge plate lifting device 10 can also be utilized highly effectively in conjunction with bridge plates employed on loading docks and similar stationary platforms where the bridge plate must be raised to a retracted or out-of-the-way position when not in use, and must be sufiiciently strong to support heavy loads as cargo is moved across the plate from the dock to a truck or vehicle, and also in the reverse direction.

Once the bridge plate lifting device 10 has been mounted in the desired location in the manner described, adjustment of tension or preloading of the torsion spring 80 may be desirable in order to obtain the type of action desired as the bridge plate is raised and lowered. Such preadjustment of the tension in the torsion spring 80 is accomplished by first engaging the projecting wrench fitting 114 of the spring anchoring hub assembly 54 with a hexagonally shaped wrench which is inserted in the hexagonal wrench socket 118 extending into the projecting wrench fitting 114. With the wrench thus engaged and firmly held by an operator, the bolts 124 are removed from the bolt holes 128 and 122 so that the spring anchoring hub assembly 54 is disengaged from the end plate 50. The spring anchoring hub assembly 54 is then free to rotate within the cylindrical housing 46, and this may be accomplished to tension the spring 80- by turning the wrench which is engaged with the hexagonal socket 118. The operator must be careful at this point not to release the wrench since the spring 80' may already be under a substantial amount of tension.

It will be understood that at such time as the operator undertakes to rotate the spring anchoring hub assembly 54 by the use of the wrench, the roller 28 carried on the upper end of the lifting arm 18 is caused to bear against the upwardly extending bridge plate 16, or some other positive stop or surface so that the lifting arm 18 cannot rotate as the tension in the torsion spring 80 is increased. The operator rotates the wrench so as to cause the spring anchoring hub assembly 54 to rotate about its central longitudinal axis. As this is done, the tension in the helical torsion spring 80 is increased by effectively winding up the spring. When enough rotation has been imparted to the spring anchoring hub assembly 54 to tension the spring 80 to a desired predetermined amount (which, incidentally, can be accurately measured by a number of suitable commercially available force measuring devices), the operator then inserts the bolts 124 through whichever of the bolt holes 122 are most nearly aligned with the bolt holes 120 in the face of the anchor plate 86 adjacent the end plate 50. It Will be recalled that the bolt holes 120 in the face of the anchor plate 86 are internally threaded so that by very slight adjustment of the position of the wrench, the bolts 124 may be threaded into these bolt holes and firm engagement of the spring anchoring hub assembly 54 with the end plate 50 obtained. The amount of tension thus set into the spring will be maintained at all times during operation of the bridge plate lifting device 10 when the lifting arm 18 is in the upward position to retain the bridge plate 16 in its inoperative or retracted position.

The bridge plate lifting device 10 of the present invention has sufficient force stored in the torsion spring 80 that the lifting arm 18 can retain the bridge plate 16 in its upwardly extending position despite relatively severe impacts transmitted through the body of the flatcar to the bridge plate at such time as the fiatcar 12 may be driven against, or bumped upon, adjacent fiatcars during coupling and switching operations. The forces tending to pivot the bridge plate 16 downwardly at such times are frequently of large magnitude, and one of the features of the present invention is the ability of the lifting device 10 to retain the bridge plate in its upwardly extending position at these times.

At such time as it is desired to utilize the bridge plate for transferring heavy loads from one fiatcar to an adjacent fiatcar, a single person may push against the upper edge of the bridge plate 16 to force it forward sufficiently to allow a predominant portion of the total weight of the bridge plate to act downwardly on the lifting arm 18. Once the bridge plate has been pushed downwardly to this extent, the total effective downward force component developed by the bridge plate will permit it to continue to move downwardly under its own weight with such downward force component effectively overcoming the opposing bias of the torsion spring 80 as transmitted to the bridge plate through the lifting arm 18. In most instances, when the bridge plate 16 has been lowered to its spanning or operative position in which the forward end of the bridge plate rests upon the adjacent fiatcar, the net downward force exerted by a bridge plate weighing from 200 to 275 pounds will be approximately 20 to 40 pounds. Thus, one person can easily lift the bridge plate upwardly enough to permit the forces stored in the torsion spring to overcome the effective or acting weight of the bridge plate, and allow the final portion of the upward movement of the bridge plate to be accomplished solely by the force acting thereon through the lifting arm 18.

The compact and sturdy construction of the bridge plate lifting device 10 of the invention permits it to function effectively over long periods of operation without being damaged by severe stresses imparted to it by vibration, shocks or impacts which are encountered by all rolling stock of railroads due to the severe and rough treatment to which such equipment is subjected. The lubrication system which is built into, and made a part of, the bridge plate lifting device assures that all bearings included in the device will be constantly lubricated and will enjoy long service life. Moreover, by virtue of the inclusion in the system of the end plate 50 and spring anchoring hub assembly 54 which can be moved relative to each other, the tension in the torsion spring 80 can be adjusted at any time so that fatiguing of the torsion spring over an extended operating life can be compensated by readjusting the pretension of the spring in the manner hereinbefore described.

A different embodiment of the invention is illustrated in FIGS. 7-9. In these figures, the bridge plate lifting device, designated generally by reference numeral 138, includes a lifting arm which differs from the lifting arm 18 utilized in the FIG. 1 embodiment of the invention in having a single elongated cylindrical shaft or rod which is utilized in place of both the tubular sleeve 42 and the lifting arm 18 utilized in FIG. 1. The lifting arm 140 includes a first end 140a upon which a roller 142 is rotatably mounted, and a second end 1401) which is extended completely through the cylindrical housing 144. The roller 142 is mounted on the end portion of the arm 140 adjacent the end 140a in identical fashion to the mounting of the roller 20 on the lifting arm 18 in the FIG. 1 embodiment. A grease fitting 146 is provided for supplying a lubricant to the roller 142 in the manner hereinbefore described.

The cylindrical housing 144 is closed at its opposite ends by a pair of end plates 148, 150 with both of these plates being centrally apertured and having an axially extending, annular bearing relief 152 formed adjacent the central aperture. Each of the bearing reliefs 152- accommodates an annular bearing or bushing 154 and a suitable sealing ring 156. A pair of spring anchoring hub assemblies and 162 are disposed inside the housing 144 at the opposite ends thereof and surround the portion of the lifting arm 140 which extends through the cylindrical housing 144. The spring anchoring hub assembly 160 includes a disc-shaped anchor plate 164 which is secured to, or formed integrally with, a hub portion 166.

The anchor plate 164 is provided with an axially extending passageway 168 adjacent its outer periphery and is relieved as shown at 170 to accommodate one end of a helical torsion spring 172 which is extended through the passageway 168. A suitable cotter key 174 or other pin is extended through the end 170 of the torsion spring 172 to secure the spring to the anchor plate 164. On the opposite side of the anchor plate 164 from the hub 166, a centrally apertured projection 176 extends through the central aperture in the end plate 148 in contact with the bearing 152 and sealing ring 156. It will be noted in referring to FIG. 7 that the spring anchoring hub assembly 160 is keyed to the lifting arm 140 by a key 180 which extends into a suitable keyway 182 formed axially in the portion of the lifting arm 140 which passes through the spring anchoring hubassembly. An annular key 184 is also provided to prevent the spring anchoring hub assembly 160 from moving axially along the shaft of the lifting arm 140.

The spring anchoring hub assembly 162 includes a bore 186 through which the end portion 140]; of the lifting arm 140 is passed, and a counterbore 188 which accommodates a hearing or bushing 190 and a sealing ring 192. A suitable annular key 194 prevents axial shifting of the spring anchoring hub assembly 162 along the lifting arm 140. The hub assembly 162 includes a disc-shaped anchor plate 196 which has projecting from one side thereof, an integrally formed hub 198, and from the opposite side thereof, a centrally bored projection 200. The projection passes through and is journaled within the bearing 154. At one of its sides, the anchor plate 196 is recessed or relieved as indicated by reference numeral 200 to accommodate an end of the helical torsion spring 172 which is extended through a passageway 202 formed through the anchor plate 146 near its outer periphery. A suitable cotter pin 204 is used to secure the spring 172 to the anchor plate 196. To assure proper spacing of the spring anchoring hub assemblies 160 and 162 despite contractions of the torsion spring 172, a spacer sleeve 197 is provided around the arm 140 and between the assemblies.

As depicted in FIG. 8, the anchor plate 196 of the spring anchoring hub assembly 162 contains a pair of diametrically opposed threaded bolt holes 206 in similar manner to the anchor plate 86 used in the embodiment depicted in FIG. 3 of the drawings. The end plate 150, similarly to the end plate of the FIG. 3 embodiment, contains a plurality of circumferentially spaced bolt holes 208 which are spaced approximately 30 of arc from each other and are positioned at substantially equal radial distances from the longitudinal axis of the elongated shaft portion of the lift arm to the radial spacing of the bolt holes 206 formed in the anchor plate 196. When the device is completely assembled, a pair of bolts 210 are extended through the two bolt holes 208 in the end plate which are aligned with a pair of bolt holes 206 formed in the anchor plate 196 of the spring anchoring hub assembly 162.

It will be noted in referring to FIG. 9 that a pair of wrench receiving slots 212 are formed on opposite sides of the bore 186 through the projecting portion 200 of the spring anchoring hub assembly 162. The purpose of the slots 212 will be hereinafter explained in greater detail.

Since the brackets utilized for mounting the cylindrical housing 144 on the forward end portion of a railroad car or on the side of a loading dock are identical to the brackets 126 and 128 utilized in the FIG. 3 embodiment of the invention, identical reference numerals have been employed to identify these brackets and the various structural portions thereof. The operation of the embodiment r of the invention depicted in FIGS. 7-9 is substantially the same as that which has been described in referring to the embodiments of the invention shown in FIGS. 36. However, in the structural arrangement shown in FIGS. 7-9, the method of setting the tension in the torsion spring 172 is slightly different from that which is utilized with the initially described embodiment. Here, a special wrench which will fit over the projecting end 14% of the lifting arm 140, and which carries a pair of protuberant prongs dimensioned to fit within the slots 212 is utilized to engage the spring anchoring hub assembly 162 in such fashion that the anchor plate 196 can be rotated to tension the spring as much as desired. A pair of bolts 214 are then inserted through a pair of bolt holes 208 in the end plate 150 which are aligned with the pair of the bolt holes 206 in the anchor plate 196. When the bolts 214 are secured in position, the anchor plate 196 is then prevented from turning, and the spring remains in constant tension until such time as a force tending to pivot the upper end of the lift arm 140 downwardly is applied to the lift arm, and thus causes the elongated shaft portion of the lift arm to be rotated about its longitudinal axis. This motion will then, of course, further tension the torsion spring 172 as the anchor plate 164 of the spring anchoring hub assembly is caused to rotate with the elongated shaft portion of the lifting arm 140. Concurrent rotation of the lift arm 140 and the spring anchoring hub assembly 160 is effected by the cooperating key and keyway 182.

In the foregoing description of the invention, it will have become apparent that this invention provides an improved bridge plate lifting device which can be relatively economically manufactured, and which is very reliable in operation, is characterized in having a long and trouble-free service life, and can be preadjusted to permit various bridge plates to be effectively raised and lowered with a minimum of manual force required.

Although certain preferred embodiments of the inven tion have been herein described in order to provide an example of the manner in which it is to be practiced for the benefit of those skilled in the art, it will be understood that various changes and modifications can be made in the depicted and described structure without departure from the basic principles of the invention. All such changes and innovations of this type which do not entail a departue from the basic principles of the invention are therefore deemed to be circumscribed by the spirit and scope of the invention except as the same may be necessarily limited by the appended claims or reasonable equivalents thereof.

What is claimed is:

1. A bridge plate lifting device comprising:

an elongated lifting arm having a first end and a second end;

an elongated, hollow housing;

an elongated member connected to the first end of said lifting arm and extending concentrically into said elongated, hollow housing, said elongated member being journaled in said housing for rotation about the longitudinal axis thereof;

first and second spring anchoring hub assemblies positioned in said housing, said first spring anchoring hub assembly being detachably connected to said housing in one of a plurality of preselected positions relative to said housing, and said second spring anchoring hub assembly being connected to said elongated member for rotation with said elongated member about the longitudinal axis thereof; and

a helical torsion spring surrounding said elongated member and having one end secured to said first spring anchoring hub assembly and the other end connected to said second spring anchoring hub assembly.

2. A bridge plate lifting device as defined in claim 1 wherein said elongated member is formed integrally with said lifting arm.

3. A bridge plate lifting device as defined in claim 1 and further characterized to include mounting brackets secured to opposite ends of said housing and having apertures therethrough facilitating securement of said mounting brackets to a stationary structure.

4. A bridge plate lifting device as defined in claim 1 wherein each of said first and second spring anchoring hub assemblies comprises:

a hub portion surrounding said elongated member and extending axially therealong inside said spring; and

a disc-shaped anchor plate extending radially outwardly from said hub portion and having a spring aperture extending therethrough adjacent the outer peripheral edge of said anchor plate for receiving one of the ends of said spring.

5. A bridge plate lifting device as defined in claim 1 wherein said elongated lifting arm is further characterized in including an end portion adjacent the second end of said lifting arm and extending substantially parallel to the axis of rotation of said elongated member; and

a roller rotatably mounted on said end portion for rotation about an axis extending parallel to the rotational axis of said elongated member.

6. A bridge plate lifting device as defined in claim 5 wherein said end portion of said lifting arm has a transverse aperture extending diametrically therethrough, and a lubricant passageway extending axially into said end portion from said second end and communicating with said transverse passageway;

and wherein said roller is axially bored to receive said end portion of said lifting arm and said bore through said roller is circumferentially grooved in a plane containing said transverse aperture;

said device being further characterized as including a helical spring in said transverse aperture; and

a pair of spherical bearings located at opposite ends of said spring and biased thereby into the circumferential groove around the bore through said roller.

7. A bridge plate lifting device as defined in claim 1 wherein said housing is a cylinder open at its opposite ends and said device is further characterized in including a pair of end plates secured in the opposite ends of said elongated cylindrical housing.

8. A bridge plate lifting device as defined in claim 7 wherein said first spring anchoring hub assembly comprises a spring anchor plate extending radially outwardly from said elongated member adjacent one of said end plates and having a plurality of circumferentially spaced bolt holes therein facing said one end plate, said first spring anchoring hub assembly being rotatably journaled on said elongated member;

and further characterized to include a plurality of circumferentially spaced bolt holes in said one end plate and each positioned for sequential alignment with each of said bolt holes in said spring anchor plate when said spring anchor plate is rotated about said elongated member.

9. A bridge plate lifting device as defined in claim 7 wherein said first spring anchoring hub assembly extends through one of said end plates to the outside of said housing.

10. A bridge plate lifting device as defined in claim 9 wherein said first spring anchoring hub assembly includes a wrench engaging portion accessible from the outside of said housing.

11. A bridge plate lifting device as defined in claim 7, wherein said end plates are centrally apertured and one of said end plates extends around said elongated memher, and the other of said end plates extends around and rotatably journals a portion of said first spring anchoring hub assembly.

12. A bridge plate lifting device as defined in claim 11 and further characterized to include a bearing lining the central aperture of each of said end plates.

13. A bridge plate lifting device as defined in claim 1 wherein said elongated member is a tubular sleeve having a first end portion journaled in said first spring anchoring hub assembly, and having a second end outside said housing and secured at substantially a right angle to said lifting arm.

14. A bridge plate lifting device as defined in claim 13 wherein said sleeve carries a transversely extending lifting arm socket outside said housing and adjacent the second end of said sleeve, and wherein said lifting arm is of circular cross section and of larger diameter than the inside diameter of said sleeve and is extended into said socket.

12 15. A bridge plate lifting device as defined in claim 13 wherein said housing is a cylinder open at its opposite ends and said tubular sleeve has a pair of axially spaced, radially extending lubricant apertures extending therethrough, said device further including a first, centrally apertured end plate closing one end of said cylinder and journaling said tubular sleeve; and

lubricant chamber defining means in said tubular sleeve defining lubricant chambers in communication with said lubricant apertures, one of said lubricant apertures extending through the portion of said sleeve adjacent said first end plate, and the other of said lubricant apertures extending through the portion 15 of said sleeve journaled in said one spring anchoring hub assembly.

16. A bridge plate lifting device as defined in claim 15 wherein said lubricant chamber defining means comprises:

a first partition cap partitioning the hollow interior of said tubular sleeve and defining with said lifting arm, a first lubricant chamber communicating with one of said radially extending lubricant apertures; and

a pair of additional partition caps partitioning the hollow interior of said tubular sleeve and spaced from said first partition cap and from each other, said additional partition caps defining between them, a second lubricant chamber communicating with the other of said radially extending lubricant apertures.

17. A bridge plate lifting device as defined in claim 16 and further characterized to include a second, centrally apertured end plate closing the second end of said cylindrical housing and having a portion of said first spring anchoring hub assembly extending therethrough, said portion of said first spring anchoring hub assembly having a wrench socket formed therein facilitating rotation of said first spring anchoring hub assembly in said housing and relative to said second end plate.

18. A bridge plate lifting device as defined in claim 17 wherein said first spring anchoring hub assembly comprises a spring anchor plate secured to said portion of said assembly and positioned inside said housing and adjacent said second end plate, said anchor plate having a plurality of circumferentially spaced bolt holes therein opening toward said second end plate, said second end plate having a plurality of circumferentially spaced bolt holes therethrough positioned for sequential alignment with each of the bolt holes in the spring anchor plate of said first spring anchoring hub assembly as said first spring anchoring hub assembly is rotated.

References Cited UNITED STATES PATENTS ARTHUR L. LA POINT, Primary Examiner R. A. BERTSCH, Assistant Examiner 

